Automatic telecommunication exchange system



May 22,1945. cs. 0. HARTLEY AUTOMAT I C TELECOMMUNI CAT ION EXCHANGE SYSTEM FiledAug. is, 1943 Inventor Patented May 22 1945 7 2,376,771 AUTOMATIC TELECOMMUNICATION EXCHANGE SYSTEM George Clifford Hartley, London, England, .as-

signorto Standard Telephones and Cables Limited, London, England, a British company Application August 16, 1943, Serial No. 498,771 r In Great Britain October 22,1942

7 Claims. (01.17.9 27) This invention relates to automatic telecommunicati'on-exchange systems and more particularly to arrangements forreceiving direct current impulses. i

The arrangements according to the present in cuiting' part of the resistanceconnected across the incoming end of said junction line in" order to send a supervisory signal to the outgoing, end, a marginal relay being connected at the outgoing end to respond thereto. I

Preferably also means is provided for automaticallyreducing the value of the biasing current for the telegraph relay after the response to the first impulse so that the first impulse is lengthened to correct for artificial shortening of the impulse which is otherwise liable to occur;

Preferably also in a. repeater for theimpulses at the incoming end of the line the impulse responding relay is separated from the contacts repeating' the impulses by means of a high pass filter which prevents surges-due to the repeating contacts from interfering with the operation of the sensitive telegraph relay, without substantially attenuating speech currents.

The invention will be better understood-from the following description of one embodiment I thereof taken in conjunction with the accompanying drawing'which shows circuits at the outgoing and incoming ends of a junction J. At the outgoing end the'junctionci-rcuits are connected to a jack adapted to be connectedto an operators cord circuit. Impulses from'the operators dial are repeated to the junction J by contacts hsl of relay HS, the manner of sending the impulses over the junction J being similar to that described in U. S. Patent No. 2,207,537, so that the growth and decay curves'of the current overthe junction J are symmetrical. Instead; however; of sending an impulse over the junction by removing a short circuit on thejunction as in specification No. 176,804, impulses are sent by placing a short circuit on the junction though either method 'of sending the impulses could be used. Thes impulses instead of being received over a transformer as described in the above" mentioned patent, are received over one winding of a polarised telegraph relay T which is connected in series with a high resistance R3 and a retard coil IL across the junction J. Thepolarised telegraph. relay. is biased by means of current in its other" '(lefthand-l winding; this winding being connected in series with resistances RI and R2 the values of which are adjusted in accordance with the resistance of the junction J so that the response on different junctions is the same, the. biasing cur rent being adjusted to be about half the current over the'junction. It will be understood that the resistance of the'junction J will depend upon the kind of junction line as well as upon its length,

being for" example less per unit length of a phantom circuit than for a side circuit.

"I'he contacts tl'of relay T ar normallyfiin spacing position due to the current'in the biasing winding; and move into marking position on the.

circuit being taken into use, the current sent over the junction overcoming the biasing. current.

During the period whilst the incoming junction circuit is waiting for the arrival of the first impulsea part of the resistance connected in. series with the biasing winding of relay T is short circuited so that the biasing current is increased.- When the impulse is received therefore relay T moves its contacts into spacing position more quickly than would be the case if the normal biasing current alone were present and the first im-' pulse is lengthened. During the first impulse the biasing current is restored to its normal value andon subsequent impulses relayT moves its contacts to spacing position under the influence of a lower biasing current than on the first impulse.

The two lines extending to the right hand side i of the drawing are connected to the normal impulse receiving circuits of a selector switch, im-

pulses being repeated thereto by contacts of relay HI whilst relays I and DI form a supervisory bridge. This is separated from relay T by a high pass filter consisting of condensers CI, 02, C3 and C5 of capacity 4 MH each in series in the line and inductance L of /2 henry inshunt. Thisgives an attenuation of db at: 500 c. p. s. and db. at 900 c. p. s. This prevents surges which arise from the operation of the selector switch circuits from aifecting the sensitive telegraph relay T, but

does notsubstantially attenuate or distort speech currents. The detailed operation of the circuit is as follows: When an operator inserts a plug into the jack on the left of the drawing relay S operates to battery on the sleeve of the jack and lights a supervisory lamp (not shown). Relay HS operates in series with. the upper winding-of relay A to earth in the operators cord circuit, whilst relay DK operates in series with the lower'wi-nding of relay A to battery in the cord circuit. Relay A operates. circuit is completed for relay SS which operates and at contacts ssl closes a locking circuit in-. dependently of contacts a'l. At contacts sail and At. front contacts sl and'al a Relay T in the incoming repeater has its con tacts tl normally biased to spacing. Onlcom circuit. Relay I operates and all contacts il; short circuits resistance RI which is inseries with the biasing winding of relay r andithis j creases the current flowing in the biasing wind 1 ing. Relay DI cannot operate at this time'be ssl a loop including windings of relay D is extended over theiijunctionv' J to the incomingre peater; relay D does not "operate in series with v the high resistance R3;

pletion of the loop the bias is overcomeqandits contacts. tl. move to marking position- Relays" B and'HI operate. Relay III at contacts ht'l con- I nects relays I and DIin, a loop acros's the selector tions automatically by means of impulses over a junction] line; including jall'first polarized telegraphrelay for receiving'said impulses, -said relay 2."System according to claim 1, in which said -means, causing. currentfiow in said biasing wind wing-includes asource of potential and a variable resistance, the value or which resistanceis adl cau'se of the presence of rectifier MBA in series I therewith and rectifier ,MRB shunting it.

. When-the operator throws the dialling -key ;in 3 her cord-circuit battery is removed from the ring of the plug and-accordingly relay DK. releases.

1 Relay DR then operates over $32 front'dkl back; At contacts-d1 1, relay HS is connected'tothetip. f

5 of the plug independently of relay jA-. I Atcon- 3 tacts drl {and (113 the outgoing junction is dis- 1 connected fromithe'cordcircuitgand battery and earth are connected to the respective-wires there i of.. At contacts cZrZ a short circuiting path forj 3 this battery and earth is prepared.

Relay HS releases in response-to the first and j subsequent circuit interruptions caused by the operators dial and at contacts-hsl short circuits battery and earth from the junction, removing v current from theright hand winding of relay T I in the incoming junction group. The bias our- 1 rent in'the left hand Winding of relay T takes 1- control and contacts tl move to spacing. Relay HI'releases and at-contactshil repeats the cuit across the relays I and DI. Relay 1 releases position against a low biasing current. This ar shorter than' succeeding impulses.

; lays I and DI and-I again operates.

. andthe cord circuit'to the'junction. 1

pulseto the 'selector.; On the first impulse'relay C operates and atcontacts-cl places a short cir-"- and at contacts 02 and ill the short. circuit across 1 resistance R! is removed, again reducing the; current inthe left hand' bias winding ofrelay. T, so that relayT operates its contacts tomarking 4 rangement ensures that the first impulse ,is not.

. Theoperator restores the dial-key; ,relay-DK 1 Operates and DR releases reconnecting .relay junction line, including. a first,po larized telegraph relay for receiving said impulses; said relay being provided with an operatingand biasing windingqrespectively,and also including .a;

At the end of the train 05f impulses relay C releases and removes the short circuit-across re- 15 When the'called subscriber; takes his receiver 3 from the hook the usual-reversal of current to 1 5 the line takes place and relay DI nowcperates'. 1 Contacts dz: short circuit resistance R3 and relay 1 D operates. resistance winding of relay DK is short circuited and an answering supervisory relay connected to At'icontacts'dl the right hand high.

1' the ring of the plug operates. Thisextinguishes.

} the supervisory lamp. When the call isfinished and the called'subi scriberplaces his receiver on the switchhook re-. lay DI releases and at contacts dil inserts resistance R3 into the loop across the junction. 1

. Relay D releases and in turn the supervisory relay in the cord circuit releases and relights the supervisory lamp.

i What is claimedis:

v The. operator removes the plug and the circuit restores to normal condition.

' l.'Telephone system for setting up connec- 3 sub-station connectedethereto.

justed in accordance with the resistance of the line' over which, the impulses are -received,; in order-to render. the response of 'sim'ilarjrelays connected tor difierentjunctions the same- 3. System according to claim 1, in which the circuit including said biasing winding. includes in seriestherewith a. resistanceand'means for short-circuitin apart of said resistance before said relay responds to the first .of said impulses,

the short circuit being. automatically removed after the response or said relay to -said first im-; pulse; soas tocause said first; impulse to be not:

shorter than succeeding;impulses., 1

4. System'accordingto claiml, and including a further circuit extending from saidjunction and means forrepeating'impulses received by said first telegraph relay to'said rfurther circuit and also including a. high pass filter separating said telegraph relay from'said impulserepeating means,whereby voice signal currents can pass. -throughq-said fi1ter,- but; signal zimpulses are blocked thereat.

5. Telephone system forsetting up .connections automatically by means of,impu1 ses over a resistance connected in series withsaid-operating windingof said telegraph relay in a loop across saidjunction; means for short-circuiting said resistance so. as to send a backward 'sup'ervisory signal, and a marginal relay: at the, outgoing end ofsaid junction; adapted torespond 7 to said supervisory signal so that supervision is maintained over said junction t-and 'a subscriber 6. Telephone system for setting',

a junction line,including a firsthpolarized telegraph relay for receiving said impulses, said; re-.= lay being provided with an operating a {biasing' winding, respectively, means fo r; causing cur-,

rent to fiow in said :biasingewindingQand impulse transmitting equipment including means. for alternately connecting battery and; earth to ..the

respective sides .of the outgoing portion of said junction and short-circuiting saidredeem d earth from said junction, whereby said..telegr aph relay isoperated by said impulses I 'I. System according; to claim 6 ,;3JlifilSOQiIl-J. eluding means by which the. battery. and earthnormally connected; ,to the respective .,sides of said junction are shortecir'cuited from said junction in response to aninterruptioniderived from said impulse transmittingeduipment, e

GEORGE emeeee' I connections automatically by. means ,of. impulsesv over; 

